U.S. Pat. No. 2,834,677 to Geisler describes a frozen sandwich which is prepared by placing a chilled (or frozen) filling between slices of frozen bread and then placing the sandwich in sub-freezing storage before the bread has thawed so as to prevent the bread from being absorbent enough to pick up any moisture from the filling. The sandwich is thawed for consumption during which it is intended that the filling will reach consumable temperature at about the same time the bread becomes absorbent, so as to minimize the amount of time, prior to consumption, that liquid filling is in contact with absorbent bread. Such a product is difficult to assemble because of the use of frozen starting materials, limits the types of fillings which can be employed and is not useful for preparing frozen products intended to be consumed after a heating step.
U.S. Pat. No. 3,532,510 to Zimmerman describes a biscuit-like product in which a filling (e.g., peanut butter, cheese, meat) is surrounded by an unbaked dough and then refrigerated. Products of this type are of little interest in the field of consumer convenience products since they require cooking by the consumer at least sufficient to cook the dough to an edible form.
U.S. Pat. No. 3,615,679 to Tangel relates to a frozen food product in the nature of a pizza in which a tomato sauce and cheese filling is enclosed between two layers of a leavened dough. The product is partially baked and then frozen, and is intended to be heated and cooked to completion in a household toaster. Toaster products of this type generally result in excessive browning of the dough portions, a condition which is acceptable for only a limited number of products.
U.S. Pat. No. 3,656,967 to Barton et al provides a toaster product having an intermediate-moisture, humectant-containing filling enveloped in a baked pastry dough crust. The moisture contents of the crust and filling are suitably balanced such that the presence of the humectant in the filling will establish a migration of water from the crust to the filling during baking to achieve a crisp flaky crust surrounding a softened filling. The disclosure does not contemplate or achieve a sandwich-bread-like covering having a crust which has a crisp texture, and a distinct crumb portion which is soft, but not soggy. This desired texture cannot be achieved using the low-moistures and toaster heating disclosed by Barton et al.
U.S. Pat. No. 3,719,138 to Blaetz and Corbige describes a "toaster" sandwich in which a filling is arranged between two slices of bread, the inner facing surfaces of the bread having been coated with a hydrocolloid to cause the filling to adhere to the bread so that the sandwich can be heated in a vertical position without loss of filling. The sandwich is frozen, after which a thin water glaze is applied to the outer bread surfaces and the product returned to frozen storage. The water glaze is intended to prevent browning of the bread during toaster heating by cooling the bread exteriors. Products of this type are not particularly practical since the preparation is involved, and the overall size of the product and the bread portions are severely limited by the size constraints of the toaster slots.
U.S. Pat. Nos. 4,020,188 and 4,171,380 to Forkner relate to products in which a frozen filling is encased by a dough having a protective backing such that the dough can be cooked without affecting the filler. The products are then refrigerated and are intended for consumption in such state.
U.S. Pat. No. 4,207,348 to Vermilyea, et al describes a sandwich-like product specially adapted for reheating with microwave energy. A frozen filling is inserted into an unbaked dough envelope and the product then proofed and baked. The baked product can then be frozen and "reconstituted", after refrigerated tempering, in a microwave oven. As the patentees note, microwave heating directly from the frozen state adversely affects the product quality.
In U.S. Pat. No. 4,400,404, a frozen pizza is prepared by encasing paste-like pizza filling ingredients in a toroidal dough, cooking the product and then freezing it. For consumption, the frozen product is further cooked at about 500.degree. F. for 15 minutes.
European Patent Application No. 0 088 361, published Sept. 14, 1983, describes a breakfast pastry in which a cooked laminated dough and roll in shortening shell encases a thickened pastry-type (e.g., fruit-flavored) filling having specified gum and starch ingredients, a moisture of 30 to 50%, a relatively low pH and a viscosity falling within specified ranges. The product is fried and then frozen and, apparently, heated in a toaster for consumption. The laminated dough is said to be important to the achievement of final product quality.
Several patents disclose heating techniques which employ conductive as well as microwave energy application; however, none are directed to the preparation of a sandwich with a high-moisture filling and an outer bread covering wherein the bread has typical fresh crust and soft, but not soggy, interior portions. Among these are British Patent Specification No. 1,506,037 which relates to a method for defrosting precooked frozen foods in which the frozen food is first subjected in a convection chamber to conductive heating followed by simultaneous application of conductive and dielectric (microwave) heating. Also, U.S. Pat. No. 4,390,555, describes a variety of sequences of defrosting and heating and provides a series of special utensils for achieving uniform complete heating of various food products. The techniques for formulating a filled sandwich of the type described herein and for heating it to achieve a fresh baked texture after months of storage are not disclosed.